Cyanoethylation of cellulose



1 2,907,625 CYANOETHYLATION or CELLULOSE No Drawing. Application March 8, 1956 Serial No. 570,214

3 Claims. (Cl. 8-120) This invention relates to an improved process for the cyanoethylation of cellulose and particularly of alphacellulose, such as cotton.

Recently, the cyanoethylation of cellulose and particularly the cyanoethylation of cotton has been of great interest because of the desirable properties which cyanoethylation confers to cotton. One of the most important properties was increased resistance to microbiological attack, such as mildew. This resistance increases with the degree of cyanoethylation, and with a degree of cyanoethylation corresponding to 3 to 3.5% nitrogen, the cotton became almost completely mildew proof. Other desirable properties were increased resistance to heat, fiat abrasion and in some cases higher tensile strength.

In the past, there were developed several general cyanoethylation processes. In one of these, the cellulose, such as cotton, is treated with an aqueous caustic alkali solution, normally of the order of 1 to 3% concentration, after which the excess solution is removed in a centrifuge and the moistened cotton then treated with acrylonitrile,

ordinarily at temperatures from 50-65 C. An excellent product was obtained, but only at the expense of very severe losses of acrylonitrile. In this process, acrylonitrile was used in large excess. For example, when a package dyeing machine is used, the amount of a'crylonitrile is about ten times the weight'of the cotton.

, United States Patent At the reaction temperature, acrylonitrile is capable of :reacting with water as well as with cellulose. The reaction with water produces a by-product beta,beta-oxydipropionitrile and therefore only a portion of the excess acrylonitrile is recovered. This loss is ordinarily referred to as the AN ratio, and is the amount of acrylonitrile lost in side-reactions divided by the amount of acrylonitrile reacted with the cotton. In the past, AN ratios as high as 5 and 6 werequite common. Thus, in spite of the excellent product produced, the process was quite costly, thereby sharply limiting the field of usefulness for the cyanoethylated cellulose.

In order to reduce the AN ratio, a so-called one-bath process was developed and is described and claimed in the copending application of Bikales, Gruber and Carpenter, Serial No. 553,446, filed December 16, 1955. In this process, where the reaction is effected in single bath the strengths of caustic alkali and excess of acrylonitrile were approximately the same as in the two-bath process described above, but they were both intimately admixed with the cellulose at temperatures at which no substantial reaction took place, and the temperature only raised to normal reaction temperature, usually in excess of 50 C., after a complete and uniform distribution of the reagents in the cellulose had taken place. This process represented a marked advance over the two-bath process and reduced markedly the AN ratios which, however, still amounted to more than 1 when nitrogen percent exceeded 3.5. This procedure was the best hitherto available, though it still consumed substantial amounts of acrylonitrile in side reactions.

weight of the cellulose.

2,907,625 Patented Oct. 6, 1959 ICC Another process is described in the copending application of Bikales, Serial No. 519,050, filed June 30, 1955,

product had other desirable characteristics, surprisingly,

the resistance to microbiological attack was nowhere near as great as in cyanoethylated cellulose produced by the oneor two-bath processes at elevated temperatures with large excesses of acrylonitrile. Thus, this process was not an answer to low cost cyanoethylated cellulose for all purposes, since its product was useful only where high resistance to microbiological attack was unnecessary.

The present invention, which is a one-bath process, produces AN ratios lower than any which hitherto have been practical, and in general, the ratios are not materially in excess of 1.2. At the same time, a product is obtained which has high resistance to microbiological attack, and so it is useful in all fields in which cyanoethylated cellulose is employed and is not restricted to those uses where mildew resistance is unimportant.

According to the present invention, a strong caustic alkali solution is used, ranging from 7 to 12%, but instead of utilizing a large amount of caustic alkali solution and a very small amount of acrylonitrile, the alkali solution is present in amounts ranging from about to about of the weight of the cellulose, and the acrylonitrile is present in large excess from 5 to 10 or more times the It is thus possible to operate in standard equipment, such as package dyeing machines, in which it is not possible to work without a volume of liquid greatly in excess of the weight of the cotton. In

\ other words, in such equipment there either has to be a large excess of caustic alkali solution or a large excess of acrylonitrile. The temperature should be kept below about 45 C. The exact temperature is not critical. Thus, for example, it is possible to contact the cellulose with the two reagents in a single bath, at substantially room temperature, maintaining approximately the temperature during reaction. The temperature may be permitted to rise somewhat. Although it is an advantage of the present invention that the temperature is not particularly critical, it is preferable to operate in the upper 30s becausethe reaction proceeds more rapidly and if care is taken not to exceed about 45 C., higher outputs can be obtained from given equipment with low AN ratios and satisfactory physical properties.

The reason for the great difference in the properties of the cyanoethylated cellulose of the present process, as compared to that produced by the process of Bikales application described above, where large excesses of caustic alkali are used with very small amounts of acrylonitrile, is not known. Chemical analysis does not show a difference. Thus, for example, the nitrogen percentage may be the same, yet one product has a high resistance to microbiological attack, while the other is only slightly more resistant than untreated cotton. Therefore, no particular theory or reaction mechanism is advanced. From a practical standpoint, however, the present invention may be said to include a combination of the advantages of both processes. For example, a very low AN ratio is obtained, even lower, in many cases, than that obtained using the low temperature, high caustic process of the Bikales application. Yet, this is achieved with the product having the desirable properties which were obtained in other processes where large amounts of acrylonitrile and higher temperatures were used.

tensile strength high in .It should be understood, of course, that the process is not limited to any particular equipment, and it should also be understood that the nature of the strong alkali is not important. For practical. purposes, of course, sodium hydroxide is so much cheaper than potassium hydroxide, that it is preferred for economic reasons, and is of course described in these examples which are representative of the best economic practice.

Example 1 yarn was wound on standard These were placed in a package dyeing machine. An amount of 9.2% aqueous sodium hydroxide solution equal to the weight of the cotton and 8 parts of commercial-grade acrylonitrile per pound of cotton yarn were circulated through the packages in the machine. The temperature rose from 25 C. to just under 40 during the course of the reaction. After the reaction was substantially complete, which took approximately 45'minutes, the reaction was stopped by neutralizing the alkali with phosphoric acid. The acrylonitrile solution was then drained from the kier and the packages washed with water. The AN ratio was approximately 0.8, that is to say more acrylonitrile reacted with the cellulose than was wasted in by-product formation. The product obtained analyzed 3.5% nitrogen. The resistance to heat and flat abrasion was excellent and the comparison to the untreated yarn. The resistance to microbiological attack as determined by the soil burial test is as shown in the following table.

of Example 1.

Tensile Strength 1 After Soil Burial Percent Initial, 2 weeks, fiweeks, 12

N g. g. weeks,

Oyanuethylated.--.. 3. 5 635 676 710 735 Untreated 0.0 585 dlslntedis.- dis.

grated...

1 Obtained on at Scott IP-2 Tester at 70 F., 65% RH.

Example 2 The procedure of Example 1 is repeated using somewhat weaker sodium hydroxide solution, namely 7.6%.

The degree of cyanoethylation was 2.8% nitrogen and the AN ratio 0.6. The product was of high quality and the resistance to microbiological action good, but not quite as high as the more highly cyanoethylated product In this respect, the difierences in resistance to microbiological attack follow in general'those of the ordinary cyanoethylated cotton, where resistance increased up to about 3.5% nitrogen, at which it remained substantially constant.

Example 3 A typical small commercial-sized run was carried out with 50 lbs. of cotton yarn. The yarn was placed in a small commercial package dyeing machine and a charge of 395 lbs. of liquid consisting of 343 lbs. of watersaturated acrylonitrile and 52 lbs. of 8% aqueous sodium hydroxide was circulated through the packages until uniform wetting took place. The temperature was then permitted to rise to 38 C. and maintained for approximately 30 minutes. Thereupon, the charge was neutralized and drained oif as described in- Example 1. A product was obtained containing 3.2% nitrogen. The AN ratio was 1.0.

We claim: a j I 1. A process for the cyanoethylation of alpha-cellulose textile fibers which comprises the steps of: treating said alpha-cellulose textile fibers at a temperature in the range from room temperature to about 45 C. with an amount of a single treating bath sufiicient to contain for each part by Weight of said fibers to be treated from about to about percent by weight of an aqueous caustic alkali solution having a concentration of from about seven to about twelve percent, and from about 5 to about 10 parts by weight of acrylonitrile, continuing said treatment until the resultant cyanoethylation and increase in nitrogen content substantially ceases, until cyanoethylated alpha-cellulose fibers having a nitrogen content corresponding to a degree of cyanoethylation of from at least about 2.5 percent to about 3.5 percent are obtained and the ratio of the weight of acrylonitrile entering into side reactions to the weight of acrylonitrile reacted with cellulose does not materially exceed about 1221.0. 7

2. A process according to claim 1 in which the alphacellulose textile fibers are cotton.

3. A process according to claim 1 in which the maximum treatment temperature is about 40 C.

References Cited in the file of this patent UNITED STATES PATENTS Dual: Textile Res. Jour., March 1955, pp. 246-253. 

1. A PROCESS FOR THE CYANOETHYLATION OF ALPHA-CELLULOSE TEXTILE FIBERS WHICH COMPRISES THE STEPS OF: TREATING SAID ALPHA-CELLULOSE TEXTILE FIBERS AT A TEMPERATUE IN THE RANGE FROM ROOM TEMPERATURE TO ABOUT 45*C. WITH AN AMOUNT OF A SINGLE TREATING BATH SUFFICIENT TO CONTAIN FOR EACH PART BY WEIGHT OF SAID FIBERS TO BE TREATED FROM ABOUT 75 TO ABOUT 150 PERCENT BY WEIGHT OF AN AQUEOUS CAUSTIC ALKALI SOLUTION HAVING A CONCENTRATION OF FROM ABOUT SEVEN TO ABOUT TWELVE PERCENT, AND FROM ABOUT 5 TO ABOUT 10 PARTS BY WEIGHT OF ACRYLONITRILE, CONTINUING SAID TREATMENT UNTIL THE RESULTANT CYANOETHYLATION AND INCREASE IN NITROGEN CONTENT SUBSTANTIALLY CEASES, UNTIL CYANOETHYLATED ALPHA-CELLULOSE FIBERS HAVING A NITROGEN CONTENT CORRESPONDING TO A DEGREE OF CYANOETHYLATION OF FROM AT LEAST ABOUT 2.5 PERCENT TO ABOUT 3.5 PERCENT ARE OBTAINED AND THE RATIO OF THE WEIGHT OF ACRYLONITRILE ENTERING INTO SIDE REACTIONS TO THE WEIGHT OF ACRYLONITRILE REACTED WITH CELLULOSE DOES NOT MATERIALLY EXCEED ABOUT 1.2:1.0. 